Help: Acid on polished limestone floor tiles

Hi all, I think this is a hopeless quest, but just in case the collective wisdom of mumsnet has any good ideas I'm posting a question here.

Our cleaner has been using an acid based cleaning product in the bathroom to get rid of limescale (in spite of having been told not to!). We have polished black limestone floor tiles in the bathroom that our landlord put in only two years ago. I wouldn't have chosen them myself because although they do look fantastic the water is extremely hard here, so they often get that white sheen on them from limescale and you can't use anything acid on them to get them clean...

Anyway, the acid seems to have taken off the top layer of the tiles and they have gone from being glass smooth to kind of scuffed.

It'll cost a fortune to replace, but we'll be here a couple more years I expect so time to try a few things - anyone have any ideas?